}
    return TCL_OK;
}

/*
 *-------------------------------------------------------------------
 *
 * KDF_Scrypt --
 *
 *	HMAC-based Extract-and-Expand Key Derivation Function (HKDF).
 *	See RFC 5869 and RFC 7914.
 *
 * Returns:
 *	TCL_OK or TCL_ERROR
 *
 * Side effects:
 *	Sets result to a list of key and iv values, or an error message
 *
 *-------------------------------------------------------------------
 */
static int KDF_Scrypt(ClientData clientData, Tcl_Interp *interp, int objc, Tcl_Obj *const objv[]) {
    EVP_PKEY_CTX *pctx;
    unsigned char *salt = NULL, *pass = NULL, *out = NULL;
    int salt_len = 0, pass_len = 0, dk_len = 64, res = TCL_OK, fn;
    uint64_t N = 0, p = 0, r = 0, maxmem = 0;
    size_t out_len;
    Tcl_Obj *resultObj;

    dprintf("Called");

    /* Clear errors */
    Tcl_ResetResult(interp);
    ERR_clear_error();

    /* Validate arg count */
    if (objc < 5 || objc > 13) {
	Tcl_WrongNumArgs(interp, 1, objv, "-password string -salt string ?-N costParameter? ?-r blockSize? ?-p parallelization? ?-size derived_length?");
	return TCL_ERROR;
    }

    /* Get options */
    for (int idx = 1; idx < objc; idx++) {
	/* Get option */
	if (Tcl_GetIndexFromObj(interp, objv[idx], command_opts, "option", 0, &fn) != TCL_OK) {
	    return TCL_ERROR;
	}

	/* Validate arg has a value */
	if (++idx >= objc) {
	    Tcl_AppendResult(interp, "No value for option \"", command_opts[fn], "\"", (char *) NULL);
	    return TCL_ERROR;
	}

	switch(fn) {
	case _opt_key:
	case _opt_password:
	    GET_OPT_BYTE_ARRAY(objv[idx], pass, &pass_len);
	    break;
	case _opt_salt:
	    GET_OPT_BYTE_ARRAY(objv[idx], salt, &salt_len);
	    break;
	case _opt_length:
	case _opt_size:
	    GET_OPT_INT(objv[idx], &dk_len);
	    break;
	case _opt_N:
	case _opt_n:
	    GET_OPT_WIDE(objv[idx], &N);
	    break;
	case _opt_r:
	    GET_OPT_WIDE(objv[idx], &r);
	    break;
	case _opt_p:
	    GET_OPT_WIDE(objv[idx], &p);
	    break;
	}
    }

    /* Create context */
    pctx = EVP_PKEY_CTX_new_id(EVP_PKEY_SCRYPT, NULL);
    if (pctx == NULL) {
	Tcl_AppendResult(interp, "Memory allocation error", (char *) NULL);
	goto error;
    }

    if (EVP_PKEY_derive_init(pctx) < 1) {
	Tcl_AppendResult(interp, "Initialize failed: ", REASON(), NULL);
	goto error;
    }

    /* Set config parameters */
    if (EVP_PKEY_CTX_set1_pbe_pass(pctx, pass, pass_len) < 1) {
	Tcl_AppendResult(interp, "Set key failed: ", REASON(), NULL);
	goto error;
    }
    if (EVP_PKEY_CTX_set1_scrypt_salt(pctx, salt, salt_len) < 1) {
	Tcl_AppendResult(interp, "Set salt failed: ", REASON(), NULL);
	goto error;
    }
    if (N != 0 && EVP_PKEY_CTX_set_scrypt_N(pctx, N) < 1) {
	Tcl_AppendResult(interp, "Set cost parameter (N) failed: ", REASON(), NULL);
	goto error;
    }
    if (r != 0 && EVP_PKEY_CTX_set_scrypt_r(pctx, r) < 1) {
	Tcl_AppendResult(interp, "Set lock size parameter (r) failed: ", REASON(), NULL);
	goto error;
   }
    if (p != 0 && EVP_PKEY_CTX_set_scrypt_p(pctx, p) < 1) {
	Tcl_AppendResult(interp, "Set Parallelization parameter (p) failed: ", REASON(), NULL);
	goto error;
    }
    if (maxmem != 0 && EVP_PKEY_CTX_set_scrypt_maxmem_bytes(pctx, maxmem) < 1) {
	Tcl_AppendResult(interp, "Set max memory failed: ", REASON(), NULL);
	goto error;
    }

    /* Get buffer */
    resultObj = Tcl_NewObj();
    if ((out = Tcl_SetByteArrayLength(resultObj, dk_len)) == NULL) {
	Tcl_AppendResult(interp, "Memory allocation error", (char *) NULL);
	goto error;
    }
    out_len = (size_t) dk_len;

    /* Derive key */
    if (EVP_PKEY_derive(pctx, out, &out_len) > 0) {
	/* Shrink buffer to actual size */
	Tcl_SetByteArrayLength(resultObj, (int) out_len);
	Tcl_SetObjResult(interp, resultObj);
	goto done;
    } else {
	Tcl_AppendResult(interp, "Derive key failed: ", REASON(), NULL);
	Tcl_DecrRefCount(resultObj);
    }

error:
    res = TCL_ERROR;
done:
    if (pctx != NULL) {
	EVP_PKEY_CTX_free(pctx);
    }
    return res;
}

/*
 *-------------------------------------------------------------------
 *
 * Tls_KeyCommands --
 *
 *	Create key commands
 *
 * Returns:
 *	TCL_OK or TCL_ERROR
 *
 * Side effects:
 *	Creates commands
 *
 *-------------------------------------------------------------------
 */
int Tls_KeyCommands(Tcl_Interp *interp) {
    Tcl_CreateObjCommand(interp, "tls::hkdf", KDF_HKDF, (ClientData) 0, (Tcl_CmdDeleteProc *) NULL);
    Tcl_CreateObjCommand(interp, "tls::pbkdf2", KDF_PBKDF2, (ClientData) 0, (Tcl_CmdDeleteProc *) NULL);
    Tcl_CreateObjCommand(interp, "tls::scrypt", KDF_Scrypt, (ClientData) 0, (Tcl_CmdDeleteProc *) NULL);
    return TCL_OK;
}